[igt-dev] [PATCH i-g-t v2] lib/xe_query: add helper getting available VRAM

[Zbigniew Kempczyński]

On Thu, Aug 03, 2023 at 01:42:32PM +0200, Lukasz Laguna wrote:
> Helper allows to read available VRAM of a specified device and GT.
> 
> v2:
> - Query for current memory usage instead of using cached one (Zbigniew)
> 
> Signed-off-by: Lukasz Laguna <lukasz.laguna at intel.com>
> ---
>  lib/xe/xe_query.c | 30 ++++++++++++++++++++++++++++++
>  lib/xe/xe_query.h |  1 +
>  2 files changed, 31 insertions(+)
> 
> diff --git a/lib/xe/xe_query.c b/lib/xe/xe_query.c
> index 8963c7b06..ef515b088 100644
> --- a/lib/xe/xe_query.c
> +++ b/lib/xe/xe_query.c
> @@ -630,6 +630,36 @@ uint64_t xe_visible_vram_size(int fd, int gt)
>  
>  	return visible_size;
>  }
> +/**
> + * xe_vram_available:
> + * @fd: xe device fd
> + * @gt: gt
> + *
> + * Returns available vram of xe device @fd and @gt.
> + */
> +uint64_t xe_vram_available(int fd, int gt)
> +{
> +	struct xe_device *xe_dev;
> +	int region_idx;
> +	struct drm_xe_query_mem_region *mem_region;
> +
> +	xe_dev = find_in_cache(fd);
> +	igt_assert(xe_dev);
> +
> +	region_idx = ffs(native_region_for_gt(xe_dev->gts, gt)) - 1;
> +	mem_region = &xe_dev->mem_usage->regions[region_idx];

I think this pointer will point out to freed mem_usage soon, so I bet:
> +
> +	if (XE_IS_CLASS_VRAM(mem_region)) {
> +		pthread_mutex_lock(&cache.cache_mutex);
> +		free(xe_dev->mem_usage);
> +		xe_dev->mem_usage = xe_query_mem_usage_new(fd);
> +		pthread_mutex_unlock(&cache.cache_mutex);
> +
> +		return mem_region->total_size - mem_region->used;

uaf will happen here (mem_region points to freed memory).

Reacquire mem_region after xe_query_mem_usage_new(fd) and this
should be good.

--
Zbigniew

> +	}
> +
> +	return 0;
> +}
>  
>  /**
>   * xe_get_default_alignment:
> diff --git a/lib/xe/xe_query.h b/lib/xe/xe_query.h
> index 1b74c58ab..20dbfa12c 100644
> --- a/lib/xe/xe_query.h
> +++ b/lib/xe/xe_query.h
> @@ -97,6 +97,7 @@ unsigned int xe_number_hw_engines(int fd);
>  bool xe_has_vram(int fd);
>  uint64_t xe_vram_size(int fd, int gt);
>  uint64_t xe_visible_vram_size(int fd, int gt);
> +uint64_t xe_vram_available(int fd, int gt);
>  uint32_t xe_get_default_alignment(int fd);
>  uint32_t xe_va_bits(int fd);
>  uint16_t xe_dev_id(int fd);
> -- 
> 2.40.0
>